Arctic Refuge: Peregrine Falcons

[This web page was created as a contribution to the "community-based ecological monitoring program" within the Arctic Borderlands Ecological Knowledge Co-op*, and follows that program's format. *There are no links from the Borderlands pages back to this web site. Use your browser's BACK button to return to the Arctic Refuge, or set a bookmark for the Refuge before you leave.]

The cliffs of the Porcupine River are an important nesting habitat for peregrine falcons. Their numbers dropped to very low levels during the 1960's and 1970's. In Alaska, peregrines of the Porcupine River are monitored by annual surveys during mid July by biologists of the Arctic Refuge. Since about 1980, the population of peregrines nesting on the Porcupine River have steadily increased, and are now at levels several times greater than during the 1960's.

The decline of peregrine falcons on the Porcupine River was part of a continent-wide decline that has been linked to the use of the pesticide, DDT. As levels of the pesticide accumulated in the peregrines, it caused thinning of their eggshells, which reduced productivity and caused populations to decline. Because of the great reduction in peregrines, they were placed on the endangered species list. Since the early 1970's, the use of DDT has been banned in both the U.S. and Canada, and the eggshell thinning problem has diminished, allowing populations of peregrines to increase as the Porcupine River data shows. In 1999, the American peregrine falcon was officially removed from endangered species status in the United States.

Production of young peregrines is also sensitive to annual variation in weather conditions. For example, colder than normal spring weather during 1989 and 1992 resulted in delayed migration of birds to the Porcupine River (See graph of young produced). The primary food of peregrine falcons are other birds, and if food is in short supply, peregrine breeding and production of young is reduced.

Peregrine falcons are at the top of the food chain and thus are very sensitive indicators of accumulation of contaminants like DDT in the environment. Because of the continuing development of new chemicals, some of which might prove to be dangerous, it is important to continue to monitor peregrine falcons as an indicator of environmental health.

The Porcupine River population of peregrines are of the subspecies: Falco peregrinus anatum or the American peregrine falcon. In Alaska, annual surveys are conducted during mid July by biologists of the Arctic Refuge.